He knew, as he slid into the building, that there was an excellent chance he would never come out, but he had to go in. He had to know what was in there, so he could plan how to defeat it. He had to know where the men of the Idaho were held prisoner and how well they were guarded and if it was possible to organize a way for them to escape. Finally, he had to know the nature of the bright beast that was always hungry, the god of the Ogrum. What was the monster that was always hungry? Some black leering idol on whose altar was daily sacrificed a living victim? Or was it something else, some real monster that the Ogrum believed to be divine? Guided by the fitful flickering of light ahead of him, Craig slipped along what was in effect an artificial tunnel. He reached the end of the tunnel, and stopped, appalled at what he saw. The temple was built like a gigantic amphitheater, like some large bowl in which athletic contests were held. Circling downward in ordered rows were tier on tier of rough stone steps. Down below him, in a huge cup that apparently rose from the solid foundation of the mountain itself was--_a seething mass of white-hot bubbling lava_! * * * * * The city of the Ogrum was located in the crater of a supposedly extinct volcano. The volcano was not extinct. It was merely inactive. Fires still seethed in its heart, and the white-hot lava, held in balance by some subterranean arrangement of pressures, bubbled up here, like a geyser that never overflows and never subsides. This bowl of lava, rising from the volcano beneath, was what Guru called the white beast that was always hungry. It was the god of the Ogrum. In a flash Craig saw why they worshipped it and why they fed human sacrifices to it. It was bright and hot like the sun. Therefore, by the laws of sympathetic magic, a sacrifice offered to the lava was the same as a sacrifice offered to the sun. The Ogrum, creatures of the dawn world, in spite of their planes and their poison gas, had no real knowledge of science, of the laws of cause and effect. The Ogrum thought that they could assure the return of the warming and life-giving sun by offering a living sacrifice to this bubbling lava! If their reasoning was erroneous and false, it was nonetheless hideous and real for all that. For they would certainly offer in sacrifice, here, every man taken from the Idaho, unless they were prevented by force. Across the arena he could see a larger opening closed by a grill of wooden poles. The flickering light from the pool of bubbling lava enabled him to see faces behind the grill--the prisoners. Involuntarily he started toward them. Then he saw the company of shaven-headed yellow clad guards standing beside the enclosure. The Ogrum were on watch!